Heretofore, multiple-layered mountaineering and survival-type lines have been known. However, their use in extremely hazardous situations has been limited by their inherent nature. For example, in the event of fire or high temperature applications, the nylon and other synthetic materials used in manufacturing such lines melt or burn, or are so severely weakened that the line becomes unusable. All too frequently, it has been determined that firemen will choose more dangerous escape routes from the upper floors of structures over a less dangerous route which requires use of a line when a flame is close by for fear the line will burn or melt, causing their fall. The choice sometimes results in the death of a trapped fireman.
Lines subjected to duty in which they come into contact with a rock outcropping or other sharp object may be severed or partially severed since the synthetic materials utilized in their construction are not highly resistant to chafing and severing. In addition, if the line is partially severed, the multiple-layer construction allows the individual layers frequently to slip along the core or relative to another, making it difficult to grasp.
Exposure to chemicals can also degrade the line and cause its failure. For safety, line is frequently discarded and not used again as a precaution if subjected to any chemicals or even if chemicals are found on the ground in the area where the line has been on the ground.
Exposure of a nylon line to ultraviolet light will break down the nylon fiber and degrade the line. For safety, nylon line is discarded after being exposed to sunlight for a period of time. The same disposal procedure is sometimes followed when a line is subjected to extreme shock.
In all of these situations, ont only is complete failure of the line possible during use, but the line when discarded may still possess sufficient strength to function adequately. Since it is impossible to determine this for a fact, and since, should the line fail, the user could be seriously injured or killed, it is general practice to incur the expense of premature disposal of the line.
Another disadvantage of conventional multiple-layer line, particularly when used for rescue, is its elasticity. During a rescue, there is frequently but one opportunity afforded to make the rescue. By using a conventional line which experiences a certain degree of stretch and bounce when under load, the timing and precision of the rescue can be adversely affected, resulting in an unsuccessful rescue attempt.
While use of a metal cable will avoid the fire/heat and severing problems, avoid the problem of exposure to chemicals, ultraviolet light and shock, and avoid the elasticity problem, cables are difficult to grasp due to their small diameter and difficult to tie and otherwise manipulate due to their unwieldly nature. Generally, a knot cannot be tied in cable which will cinch tightly enough to hold and be safe. It is not possible to increase the diameter of the cable to facilitate grasping of the cable due to weight and other considerations, and doing so would make tying of knots even more difficult. Another problem with metal cable is that its outer surface is sometimes too slippery to be securely grasped, making for an unsafe condition, and is sometimes too abrasive to be safely handled, depending on the type and condition of the cable.
Another serious disadvantage when using a metal cable, should the cable snap under load, is that the inherent whip or backlash causes the severed and loose ends of the cable to be propelled, sometimes at great speed, toward the source of the load. The ends generally flail about as they fly through the air and can cause great injury and even death to the cable user and bystanders. Of course, if the severing results in a fall of the user, injury or death could also result. While described herein for wire cables, the backlash problem exists for synthetic ropes also.
It is an object of this invention to provide a lightweight, manipulatable, easy-to-grasp line of relatively high strength for use such as by mountaineers, firemen and others. The line should be a static line without significant stretch. Exposure to fire/heat, sharp objects, chemicals, sunlight or shock should not produce failure of the line or require its premature disposal. If the load-carrying limits of the line are exceeded, it should not fail completely and dangerous backlash should not occur. Even if the line is severed completely, backlash should be minimized. It is another object of this invention to provide a line having a plurality of braided or woven layers which are resistant to axial movement along a core and each other.